Development of Solid Electrolytes Using a Combined in-Operando XPS-Theroetical Approach

锂离子电池系统开始接近其性能的理论极限，因此，新锂离子技术的发展越来越依赖于对表面化学及其对电化学响应的影响的深入了解。为了使可再生能源技术更加广泛地应用，继续开发安全、可扩展和可靠的能源存储方法至关重要。电池系统是界面设备，界面处发生的化学过程对电池的整体性能和容量至关重要。X射线光电子能谱（XPS）等技术对推进我们对表面和界面化学的理解越来越重要。XPS有助于跟踪电极材料在充放电循环过程中的氧化态变化，并能熟练地检测化学环境的变化和界面处新物种的形成。电池的循环导致阳极上固体电解质界面（SEI）的发展。这种电子绝缘但离子导电的薄膜由电解质分解产物组成，其对电池性能的影响因组成而异，可能限制或增强整体功能。表面敏感技术能够表征电池界面，XPS是表面敏感的，因为光电子只能从样品表面区域逃逸，而不会损失能量和特定的化学和电子信息。In-Operando研究通过观察和比较XPS峰的位移，可以了解固态电池中形成界面的生长、组成和动力学。位移可以归因于氧化态的变化、化学环境的变化、由于样品掺杂或施加电势的存在而导致的能级的变化。当与其他表面敏感技术一起使用时，可以获得关于样品的广泛信息。FTIR和拉曼光谱等技术可用于进一步了解阴极处发生的化学反应以及充电或放电时形成的物质的性质。将实验数据与计算研究进行比较将有助于评估峰位移的原因，作为态密度和XPS光谱的理论数据，可以获得，并将其与通过使用In-电池循环的操作和尸检研究。DFT可以提供材料化学性质的关键见解，并可用于评估电池材料的可行性。分子动力学模拟还将显示界面形成动力学的关键见解。该项目的初步目标是用这种新技术比较和再现现有固体电解质的结果，从锂镧钛氧化物和锂镧锆氧化物开始，重点是避免XPS数据中的伪影和再现准确的电化学数据，这提供了有关容量的信息，容量衰减、氧化还原电位和其他电池数据。通过关注充电和放电速率，因为这会改变所形成的化合物和电池的整体性能，可以提高对电池动力学和界面形成的理解，并且结果可以应用于开发新的电解质材料。然后可以研究改变现有固体电解质对电池性能的影响，例如卤化作用的影响，并将其应用于生产新材料，如硫化物和复合固体电解质材料。

Lithium-ion battery systems are beginning to approach the theoretical limits of their performance and as a result, developments in new Li-ion technologies are becoming increasingly more dependent on gaining a deeper understanding of surface chemistry and its impact on electrochemical response. For renewable energy technologies to become more widely available, it is pertinent that safe, scalable, and reliable methods of energy storage continue to be developed. Battery systems are interface devices and the chemical processes occurring at the interfaces are crucial to overall performance and capacity of the battery.Techniques like x-ray photoelectron spectroscopy (XPS) are increasingly crucial for advancing our understanding of surface and interface chemistry. XPS facilitates the tracking of electrode material oxidation state changes during charge and discharge cycles, and it adeptly detects alterations in chemical environments and the formation of new species at interfaces.Cycling of the battery induces the development of a solid-electrolyte interface (SEI) on the anode. This electronically insulating yet ion-conductive film consists of electrolyte decomposition products, and its impact on cell performance varies based on composition, potentially limiting, or enhancing overall functionality. Surface sensitive techniques are capable of characterising battery interphases, and XPS is surface sensitive as photoelectrons can only escape the sample from the surface region without losing energy and specific chemical and electronic information.In-Operando studies allow for understanding of the growth, composition, and kinetics of forming interphases in solid-state batteries through observation and comparison of shifts in observed XPS peaks. Shifts can be attributed to changes in oxidation state, changes in chemical environment, changes to the energy levels due to sample doping of presence of an applied potential. When used alongside other surface- sensitive techniques, a broad range of information can be obtained about a sample. Techniques such as FTIR and Raman spectroscopy can be used to further understanding of the chemistry occurring at the cathode and the nature of and species formed upon charging or discharging.Comparison of experimental data to computational studies will allow for evaluation of the causes of peak shifts, as theoretical data for the density of states and XPS spectra can be obtained and compare this to what experimental findings through use of in-Operando and post-mortem studies of battery cycling. DFT can give key insights into chemical properties of materials and can be used to assess viability as battery materials. Molecular dynamics simulations will also show key insights into the kinetics of formation of interphases.Initial aims of the project are to compare and reproduce results of existing solid electrolytes, starting with lithium lanthanum titanium oxide and lithium lanthanum zirconium oxide, with this new technique, focusing on avoidance of artefacts in the XPS data and reproduction of accurate electrochemical data, which gives information about capacity, capacity fading, redox potential, and other battery data.From focusing on charge and discharge rates, as this alters the compounds formed and the overall performance of the cell, understanding of dynamics of the cell and interphase formation can be improved, and the results can be applied to developing new electrolyte materials. The effects of alterations to existing solid electrolytes, for example to effect of halogenation, on the performance of the cell can then be studied and applied to production of new materials such as sulfides and composite solid-electrolyte materials.